Automobiles have been equipped with more and more electrical and electronic components for the compliance with environmental regulations and for the pursuit of comfort and safety, and this requires further narrower pitches and further smaller sizes typically of terminals/connectors and relaying components to be used in the automobiles. Similar requirements have been also made in information communications and household products. For these uses, Cu—Ni—Si alloys have been widely used, because the alloys simultaneously have high strength, high thermal stability, high stress relaxation resistance, and relatively high electric conductivity.
With the down-sizing of electrical and electronic components, more demands have been made on copper alloy sheets for use in electrical and electronic components to have not only high strength and high electric conductivity but also excellent bending workability so as to endure 180-degree bending or 90-degree bending after notching. Additionally, with the down-sizing of electrical and electronic components, severe bending is often conducted in a bend line in parallel to the rolling direction, so-called “bad way” (B.W.), whereas conventional severe bending has been conducted in a bend line transverse to the rolling direction, so-called “good way” (G.W.).
Patent Documents 1 to 5 mentioned below disclose techniques for improving the bending workability of Cu—Ni—Si alloys both in G.W. and B.W.
Specifically, to improve the bending workability, the techniques disclosed in Patent Documents 1 and2 specify the compositions of Cu—Ni—Si alloys and conditions for working and heat treatment; the technique disclosed in Patent Document 3 controls the degree of accumulation of crystal orientation in the sheet surface; the technique discloses in Patent Document 4 specifies the ratio of yield stress to tensile strength, the ratio of uniform elongation to total elongation, and the work hardening coefficient; and the technique discloses in Patent Document 5 controls the electric conductivity and the yield stress in directions in parallel to and transverse to the rolling direction after solution annealing and specifies the processing rate (reduction ratio) in finish cold rolling after solution annealing.
Patent Document 1: Japanese Unexamined Patent Application Publication (JP-A) No. 59505/1993
Patent Document 2: JP-A No. 179377/1993
Patent Document 3: JP-A No. 80428/2000
Patent Document 4: JP-A No. 266042/2002
Patent Document 5: JP-A No. 219733/2006